The subject invention relates to a reel-to-reel handler employed in automatic test systems, and is designed to automatically test under environmental conditions reeled axial-lead devices such as diodes, resistors, capacitors, inductors, small-signal transistors, and SCRs.
Reeled axial-lead devices generally include a linear array of electrical components having opposed axial leads that are connected or encapsulated in elongated carriers, generally made of two parallel strips of tape material. The tape carriers maintain the axial-lead devices in spaced parallel relationship along the length of the tapes, and the resulting taped components are wound about a reel, with the layers of the components being separated by a strip of paper. Heretofore conventional reel-to-reel automatic electrical test handlers operated to sequentially test the axial-lead devices under ambient temperature conditions, or, it has been known to completely place the entire reel-to-reel handler within a large chamber, and heat the chamber to the desired environmental temperature conditions preparatory to the electrical testing of the electrical components. As is readily apparent, because of the fact that the component leads are merely connected to the tape carriers by the adhesive on the tape, when subjected to elevated temperatures, the adhesive on the tape softens, thereby causing the axial-lead devices to move, become misaligned, and possibly become disengaged from the tape carriers. In addition to the problem associated with the disengagement of the electrical components from the tape, since the entire reel-to-reel handler is disposed within the environmental chamber, it is difficult for operators to use the apparatus because of the heat generated within the chamber, and accordingly it takes a relatively long period of time for the operator to install and remove reels of components to be tested. In addition, with each removal and installation of a reel, the operator must wait a sufficient period of time in order to enable the apparatus to be brought up to desired environmental test conditions. The desirability for testing the reeled axial-lead devices under environmental conditions is particularly important in more sophisticated electronic systems, and in those applications wherein the components are to be embodied in apparatus which operates under either higher temperature conditions or lower temperature conditions than ambient. Examples of those conditions are electrical apparatus which are employed in a box radio, an automobile, or any sealed case wherein the temperature goes above or below normal room temperature.
Another shortcoming of prior art reel-to-reel handlers results from the arrangements provided in such prior art handlers for conveying the devices to the testing station. In one apparatus, the mechanism for moving the taped component is performed by a motor which moves a cam that, in turn, moves an entire track which shuttles or carries the components along in a sequential manner. The track is configured to include a plurality of upstanding walls, whereby the adjacent axial-leads are disposed within the spaces defined intermediate the upstanding walls. The track is moved in a circular movement, to effectively lift the entire reel, and at the same time, project the reel forwardly to the equivalent of one spacing of the electrical components, and at the completion of its circular movement, the track then engages the next, or downstream, set of electrical components. During the upward movement of the track, a fowardmost electrical component is forced into contact with the test contacts of the electrical tester, and at that time said forwardmost component is tested. In order to achieve precise feeding of the axial-lead components, it is apparent that the track mechanical structure must be precision made, thereby resulting in the relatively high cost of the prior art reel-to-reel handler. In addition, because of the weight and inertia of the movable track, that is continuously operated through a circular path, the speed of operation of the prior art handler must be limited in order to limit the amount of vibration generated by the constantly moving mass of the track, thus limiting the speed of operation of the prior art handler. Another shortcoming of the prior art device is that no means are provided for ensuring that a space left in the reel of components, such as by the removal of an electrical components, prior to the testing station, will not be moved by the track into position beneath the test points. In other words, if an electrical component is removed from the reel prior to testing, that portion of the tape would still be forced by the movable track beneath the testing station, and the test would, of course, result in a reading that a defective part exists at that point. Usually, reel-to-reel handlers are designed such that after a certain number of defective parts are detected, the machine is automatically stopped. Thus, it is possible that the prior art device may be inadvertently shut down, not because the reel contains a certain number of defective parts, but because a certain number of electrical devices had been removed from the reel prior to being positioned on the reel-to-reel handler. The inadvertent stoppage of prior art handlers thereby results in lost testing time, as well as the necessity for the operator to continually monitor the operation of the apparatus.